NAME

SYNOPSIS

DESCRIPTION

add_key() asks the kernel to create or update a key of the given type
and description, instantiate it with the payload of length plen, and to
attach it to the nominated keyring and to return its serial number.
The key type may reject the data if it’s in the wrong format or in some
other way invalid.
If the destination keyring already contains a key that matches the
specified type and description then, if the key type supports it, that
key will be updated rather than a new key being created; if not, a new
key will be created and it will displace the link to the extant key
from the keyring.
The destination keyring serial number may be that of a valid keyring to
which the caller has write permission, or it may be a special keyring
ID:
KEY_SPEC_THREAD_KEYRING
This specifies the caller’s thread-specific keyring.
KEY_SPEC_PROCESS_KEYRING
This specifies the caller’s process-specific keyring.
KEY_SPEC_SESSION_KEYRING
This specifies the caller’s session-specific keyring.
KEY_SPEC_USER_KEYRING
This specifies the caller’s UID-specific keyring.
KEY_SPEC_USER_SESSION_KEYRING
This specifies the caller’s UID-session keyring.

KEYTYPES

There are a number of key types available in the core key management
code, and these can be specified to this function:
“user” Keys of the user-defined key type may contain a blob of
arbitrary data, and the description may be any valid string,
though it is preferred that the description be prefixed with a
string representing the service to which the key is of interest
and a colon (for instance “afs:mykey”). The payload may be
empty or NULL for keys of this type.
“keyring”
Keyrings are special key types that may contain links to
sequences of other keys of any type. If this interface is used
to create a keyring, then a NULLpayload should be specified,
and plen should be zero.

RETURNVALUE

On success add_key() returns the serial number of the key it created or
updated. On error, the value -1 will be returned and errno will have
been set to an appropriate error.

ERRORS

ENOKEY The keyring doesn’t exist.
EKEYEXPIRED
The keyring has expired.
EKEYREVOKED
The keyring has been revoked.
EINVAL The payload data was invalid.
ENOMEM Insufficient memory to create a key.
EDQUOT The key quota for this user would be exceeded by creating this
key or linking it to the keyring.
EACCES The keyring wasn’t available for modification by the user.

LINKING

Although this is a Linux system call, it is not present in libc but can
be found rather in libkeyutils. When linking, -lkeyutils should be
specified to the linker.